Bitcoin/public point to address: Difference between revisions
Bitcoin/public point to address (view source)
Revision as of 18:14, 30 September 2013
, 10 years agoGo solution
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return 0;
}</lang>
=={{header|Go}}==
<lang go>package main
import (
"crypto/sha256"
"encoding/hex"
"errors"
"fmt"
"code.google.com/p/go.crypto/ripemd160"
)
// Point is a type for a bitcoin public point.
type Point struct {
x, y [32]byte
}
// SetHex takes two hexidecimal strings and decodes them into the receiver.
func (p *Point) SetHex(x, y string) error {
if len(x) != 64 || len(y) != 64 {
return errors.New("invalid hex string length")
}
if _, err := hex.Decode(p.x[:], []byte(x)); err != nil {
return err
}
_, err := hex.Decode(p.y[:], []byte(y))
return err
}
// A25 type in common with Bitcoin/address validation task.
type A25 [25]byte
// doubleSHA256 method in common with Bitcoin/address validation task.
func (a *A25) doubleSHA256() []byte {
h := sha256.New()
h.Write(a[:21])
d := h.Sum([]byte{})
h = sha256.New()
h.Write(d)
return h.Sum(d[:0])
}
// UpdateChecksum computes the address checksum on the first 21 bytes and
// stores the result in the last 4 bytes.
func (a *A25) UpdateChecksum() {
copy(a[21:], a.doubleSHA256())
}
// SetPoint takes a public point and generates the corresponding address
// into the receiver, complete with valid checksum.
func (a *A25) SetPoint(p *Point) {
c := [65]byte{4}
copy(c[1:], p.x[:])
copy(c[33:], p.y[:])
h := sha256.New()
h.Write(c[:])
s := h.Sum([]byte{})
h = ripemd160.New()
h.Write(s)
h.Sum(a[1:1])
a.UpdateChecksum()
}
// Tmpl in common with Bitcoin/address validation task.
var tmpl = []byte("123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz")
// A58 returns a base58 encoded bitcoin address corresponding to the receiver.
// Code adapted from the C solution to this task.
func (a *A25) A58() []byte {
var out [34]byte
for n := 33; n >= 0; n-- {
c := 0
for i := 0; i < 25; i++ {
c = c*256 + int(a[i])
a[i] = byte(c / 58)
c %= 58
}
out[n] = tmpl[c]
}
i := 1
for i < 34 && out[i] == '1' {
i++
}
return out[i-1:]
}
func main() {
// parse hex into point object
var p Point
err := p.SetHex(
"50863AD64A87AE8A2FE83C1AF1A8403CB53F53E486D8511DAD8A04887E5B2352",
"2CD470243453A299FA9E77237716103ABC11A1DF38855ED6F2EE187E9C582BA6")
if err != nil {
fmt.Println(err)
return
}
// generate address object from point
var a A25
a.SetPoint(&p)
// show base58 representation
fmt.Println(string(a.A58()))
}</lang>
{{out}}
<pre>
16UwLL9Risc3QfPqBUvKofHmBQ7wMtjvM
</pre>
=={{header|Perl}}==
| |||